As the height continues to decrease, there is a force reversal. Studies performed by Ranzenbach and Barlow [ They performed experiments and numerical studies on symmetrical and cambered airfoils. They had found out that the lift force reaches a maximum at a ground clearance of approximately 0. This explains the reduced lift force at very close distance to the ground.
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There were two objectives of the study reported on; firstly to verify the Finite- Analytic Navier-Stokes computational approach by comparing the computational results for the case of a stationary airfoil at various heights above ground to experimental results, and secondly to examine the force reversal phenomena for the specific case of a NACA airfoil. This technique solves the whole flowfield including that near the wall.
The author comments that the usefulness of this technique is that the dependent variables remain at the grid nodes and the mass and momentum are conserved at every time step. A recent paper by Barber  noted that areas of uncertainty due to the problematic nature of experimental and numerical simulation still exist in demonstrating the effect of and common assumptions made in modeling ground effect aerodynamics.
Barber calls for an integrated study, making use of both experimental and numerical techniques. Where using numerical simulation is the only feasible option, say for examining the effect of the aerodynamic pressure on the water surface, it should nevertheless be backed up by a systematic study of similar experiments.
Aero-and Hydro-dynamic Basics of WIG Craft Useful research works which have been published in the field of hydrodynamics of planing hull and aerodynamics of wings are reviewed. The experimental work of Clement et al.
The work developed by Savitsky, [79 and 80], on the prediction of planing hull performance and the development of Blount factor to modify Savitsky method for better prediction of Series 62 models resistance is reviewed . Savitsky mathematical model of planing hull hydrodynamics, predicts the required hull power and performance . Savitsky and Brown , had modified that mathematical model by adding fixed slope flap to the prismatic hull in order to control hull trim angle and eliminate proposing phenomenon. The flap lift and drag forces were added to the equilibrium equation, where the flap moment is applied to control trim.
Denko  had modified that mathematical model by adding aerodynamic lift and drag forces for planing hull and its superstructure. Hadler  had also modified Savitsky planing hull mathematical model by adding the effect of hull appendage and propeller lift and drag forces to the hull equilibrium equation. Fox and Blount,  have also modified the method by adding a correction factor to apply when the hull has a non-prismatic form. For aerodynamic forces, Kerwin,  had presented empirical equation to determine the lift and drag force for the airfoil sections at different angles of attack.
This equation can be used to determine the lift and drag force for the wing and tailplane.
Aerodynamic Lift - How Airplanes Fly
Tomasz , represents numerical investigation about airfoil in ground effect, showing the increase in lift coefficient in ground effect. Empirical equation equation 1. Summary of Literature Review and Objectives of Thesis 1. Experimental and numerical approach are the available tool in predicting the performance of WIG crafts, which may consuming time and work especially at predesign stage. Aerodynamic design of wing geometry is considered one of the most critical tasks until now. Many researchers call for establishing new series specialist in ground condition.
The most important parameters in ground effect are focus on the shape of lower and upper surface which needed to clarify in most standard series description. NACA airfoils are described by maximum thickness, camber and potion of maximum thickness only. Thesis Objectives The main aim of the thesis is to improve WIG craft efficiency by developing its wing design.
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Design airfoil section shape suitable to extreme ground condition, designed to fitted in WIG craft which not need to large range of angle of attack in its operation operate close to water. This aim can be archive by divided it to many sub-objectives such as: 1. Review of ground phenomena and its boundary conditions.
Review of airfoils section parameters which affect aerodynamic efficiency. Built numerical model for airfoil section in both ground and unbounded conditions able to evaluate the lift, drag and moment and also, simulate the flow around the airfoil body. Study the effect of change airfoil design parameters on aerodynamic efficiency for NACA 4-digit family as a basic form.
Propose a method to identity the parameters which are defaults in standard series such as location of maximum thickness and the shape of lower and upper airfoil surfaces.
(PDF) Efficiency of Wing-In-Ground Marine Crafts | Islam Amin - adapmotmiref.ga
Design new airfoil section suitable to ground condition from the parametric study. Developing method to predict the efficiency of WIG craft and other performance data to use it in evaluate the new airfoil section with sample method. Methodology of Research 1. Statistical approach is used to obtain the design aspects of WIG craft, such as wing, stabilizer, and hull aspects, which can helped in build mathematical model.
Numerical approach to simulate the flow around airfoil in both ground and unbounded conditions. Mathematical approach is used to develop predicting method based on aero- and hydro-dynamic concept suitable to evaluate the efficiency of WIG craft with new airfoil section. Comparative approach is used to validate the proposed numerical and mathematical models with pervious experimental work. Assumptions of Research: 1.
Thesis mathematical model of WIG craft, simulate airplane configuration only. The model is considered as with class A which makes it competence of IMO classification. And the author assumes that the range limit is up to 4 degrees. The WIG fuselage is prismatic shape like to planing hull shape. The wings and stabilizers shapes which used in thesis are rectangular shape with large aspect ratio studded by 2-D methods.
The relation between aerodynamic and hydrodynamic forces is in linear relation. Highlight on some Facts 1. The thesis focuses on improving WIG craft efficiency by developing its wing section. So study interest with airfoil section shape in ground effect condition only. Aerodynamic efficiency expressed by lift per drag ratio. Improving the efficiency of WIG craft mean in this thesis, the reduction in power consumption which can be achieved by improving the aerodynamic efficiency of its wing.
Collected data from 50 WIG units that already exist in marine market is presented. Some important design aspects of WIG craft are introduced briefly aiming to indentify simple guideline to WIG craft designers. Also, this introductory information about WIG design aspect is used to build mathematical model which is presented in Chapter 5.
The best solution will depend on the specifications required for the crafts operation and its type.
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Wing The wing design of WIG craft is defined by the planform and the cross sectional shape. Each of these parameters affects the aerodynamic behavior and performance of the craft.
The most common planform shape configurations are delta, rectangular, tandem and ram wing. The delta wing was researched by German physicist Alexander Lippisch because of its wing shape that allows stable flight in ground effect, . The advantage of the delta wing is its self stabilizing; this shape is the main form of type B ground effect craft.
The canard style design improves the take off efficiency as it creates an air cushion to lift the craft above the water at lower speed, thereby reducing water drag, which is the crafts biggest problem .
The planform shape depends on the desired maneuverability and speed of the craft. Flight maneuverability is governed by the span length. A large span requires the craft to attain a higher altitude before making a turn to avoid contact with the water. The efficient height range for ground effect flight is largely dependent on the chord of the wing.